将子查询结果设置为默认值

Question

I want to do the next:

ALTER TABLE bets 
ADD COLUMN owner_id bigint NOT NULL DEFAULT (SELECT min(user_id) FROM users);

I'm confused postgres does not allow to save SELECT min(user_id) FROM users subquery's result to a variable and then reuse it.

Any ideas how to set subquery result as default value?

PS bets table is not empty

Answer 1

This seems to work for me:

create function my_foobar_default(OUT id uuid)
as 'select id from foobar order by X desc limit 1'
language sql

alter table Y
add column if not exists SOMEVALUE uuid not null default my_foobar_default()